Dante Exum received an early 19th birthday present with the Utah Jazz signing him to a $US3.6 million ($3.91 million) first-year contract.

The contract came on the eve of his first game for the Jazz in the NBA Summer League in Las Vegas and ahead of Sunday's birthday.

"Officially a member of the Jazz," Exum wrote in a tweet accompanied by a photo of him signing the contract.

Exum, who less than a year ago was a high school student in Canberra, has also signed major contracts with Adidas and Red Bull. After skipping US college basketball and months of hype ahead of the NBA Draft where he was selected fifth by the Jazz, the man dubbed the "International Man of Mystery" will don a Jazz singlet against the Philadelphia 76ers in Las Vegas on Saturday (Sunday AEST) for his first professional game.

But, James returning to the Cavs could mean the exit door for Dellavedova. Cavs management is also in pursuit of Minnesota power forward Kevin Love and may package Dellavedova and other players to trade for Love or create salary space to secure the All-Star.

Dellavedova will earn a relatively small $US816,000 ($A883,000) the coming season, but starred on Friday for the Cavs in their first Summer League game against the Milwaukee Bucks. The Victorian point guard had 13 points, nine rebounds and six assists from a game high 36 minutes on the court and dropped two high pressure free throws in the final seconds to secure a 70-68 win.

The Cavs would love to keep Dellavedova, but the team's priority is to create salary space to surround James with Love and other veterans who have NBA Championship experience.

Melbourne United sharpshooter Chris Goulding did not have a great debut for the Dallas Mavericks in their 76-64 loss to the New York Knicks in Las Vegas. Goulding, who is hoping to score a contract with the Mavericks or other NBA teams, started for the Mavericks but was off target, hitting just two of eight shots to finish with six points and two turnovers.

Another Aussie, 217cm centre Jordan Vandenberg, is on the Knicks' Vegas squad but did not leave the bench. Summer League allows NBA teams to play their recent draftees, reserves and free agents in the off-season before the 2014/15 season tips off in October.